Ben Barba's much-anticipated Super League debut ended in defeat as St Helens suffered a damaging 26-16 loss to arch rivals Wigan Warriors in the Super League Super 8s.
Both teams headed into Friday's match at the Totally Wicked Stadium one point outside the top four, knowing they could ill afford to be beaten.
Saints were boosted by the inclusion of Barba, the former NRL star available following a 12-match drugs ban, but the full-back was at fault for Oliver Gildart's second try as the Warriors raced into a 12-0 lead inside six minutes.
Although Barba claimed a try of his own, 2016 champions Wigan remained in front thereafter to earn a vital two points in their title defence.
Shaun Wane's Warriors remain one point behind fourth-placed Wakefield Wildcats in the race for a semi-final place, with Saints now three off the pace with three rounds to go.
Wakefield thumped Salford 43-18 to effectively end the Red Devils' hopes of making the top four, while Huddersfield Giants are out of the running after giving up a 12-6 half-time lead to lose 24-16 to Castleford Tigers, who have already secured the League Leaders' Shield.